General
FIG. 1 shows the UMTS protocol architecture of layer 2 and lower layer 3 (for the layer model, see [1]), which contains the protocols of the UMTS radio interface. This architecture exists both in the mobile device (User Equipment, UE) and also in a node of the mobile communication network (Radio Network Controller, RNC); in other words, each of the protocols exists once in the UE and once in the RNC.
The same protocols exchange Protocol Data Units (PDUs), as they use the services of the protocol layers below them for the transport of PDUs. Every protocol layer provides the layer above it with its services at what are known as service access points. To understand the architecture better, these service access points are given commonly used and unique names; e.g., logical channels, transport channels, Radio Bearer. For data transfer, protocols pick up service data units (SDUs) at their service access points and transmit PDUs generated from these to the layer below them, so PDUs from upper layers are identical to the SDUs of the layer below.
The protocol layers shown in FIG. 1 are                the Radio Resource Control (RRC) layer        the Packet Data Convergence Protocol (PDCP) layer        the Broadcast/Multicast Control (BMC) layer        the Radio Link Control (RLC) layer        the Medium Access Control SAC) layer        and the physical layer (PHY).        
As the PDCP and BMC layers have no specific significance for this invention disclosure, they are not described in any more detail here. The functions of RRC, RLC and MAC are described briefly and generally below. There follows a more precise description of those functions which should be improved or modified via the present invention.